Thursday, September 23, 2010

Whale Shark Paternity Study Comparison

The two articles under review for this particular assignment are “Whale Sharks May Produce Many Litters from One Mating, Paternity Test Shows” (Science Daily Staff, 2010) which will be acting as the piece of secondary literature for this assignment and the piece of literature acting as the primary literature will be “Paternity analysis in a litter of whale shark embryos” (Jennifer V. Schmidt1, 2,*, Chien-Chi Chen3, Saad I. Sheikh4, 8, Mark G. Meekan5, Bradley M. Norman6, 7, Shoou-Jeng Joung3, 2010.). As is clearly stated in the titles of both the primary and secondary literature the object of study is the breeding habits of whale sharks. To complete this study a single whale shark was analyzed containing 304 embryos which was caught near Taiwan in the year of 1995 (Schmidt 2010.) Of these 304 embryos 29 embryos of all different ages were studied to determine if they had an identical father (Schmidt, 2010.)

The secondary article “Whale Sharks May Produce Many Litters from One Mating, Paternity Test Shows” (Science Daily Staff, 2010) is a typical article one would find in a newspaper or on an online website such as the one this particular article was found on (www.sciencedaily.com). The article summarizes key facts and important data from within the study and then presents it in an easy to understand format for the general public to view. This easy to read format intrigues the public more so than a scientific paper would and thus allows them to become more interested in the subject presented by the secondary article. This format works well for the general public but for the more intrigued person, such as an environmental science student, a more detailed analysis and understanding of the study is needed. Hence we look to the primary article for more information. In this blog several points from within the secondary article will be analyzed and compared with the primary article to see just how true to the study the secondary article is.

The first example that will be examined is the point made in the secondary article where the author reveals the primary result of the study. As written by the author of the secondary article the primary result of the study showed that the 29 embryos of all different ages did in fact have an identical father (Schmidt, 2010.) Although the author presented the same primary result shown in the primary article they neglected to explain exactly how this result was determined. As it turns out the process to identify whether the embryos had an identical father was very tedious. The way the scientists determined whether or not the embryos had an identical father was by comparing the genotypes of the embryos using 9 microsatellite loci (Schmidt, 2010.) The scientists predicted that if the 9 microsatellite loci showed more than 4 alleles that there would be more than one father for the litter but if the 9 microsatellite loci contained 4 alleles than the litter would likely have an identical father (Schmidt, 2010.) After the DNA was sequenced and the 9 microsatellite loci were compared the results concluded that all of the microsatellite loci contained only 4 alleles (Schmidt, 2010.) This result indicated that there was a very high likelihood that the 29 embryos contained an identical father. This primary result was shown in the secondary article but it failed to explain the process in which the result was determined. The secondary article also failed to mention the error within the experiment. This error accounted for the fact that only 29 out of 304 embryos were tested. The fact that only a percentage of the embryos were tested for paternity makes it impossible to state that all of the embryos came from an identical father (Schmidt, 2010.) A probability analysis showed that there could have been a second undetected father if it was responsible for breeding a number of embryos totalling fewer than 10% (Schmidt, 2010.)

The second example that will be compared between the two articles is the secondary part of the results of the experiment where by the study concludes that there is a possibility that a whale shark can store sperm from a single mating and then use this sperm to fertilize eggs during a length of time (Schmidt, 2010.) This hypothesis could explain the reason why there is such a variety in the ages of the embryos (Schmidt, 2010.) The secondary article presents this hypothesis in the form of a quote from Schmidt where she says, "We have to be very cautious in drawing conclusions from a single litter, but the data suggest female whale sharks store sperm after a single mating event, and subsequently fertilize their own eggs as they are produced." (Schmidt, 2010.) Although the author of the secondary article expresses the results of the study in the form of a quote straight from one of the people involved in the study, it still does not provide the full detail involved in the study that led to that particular hypothesis. In the primary article scientists explain how it is possible for sharks to store sperm. Sharks contain an oviducal gland and this is the site of sperm storage (Schmidt, 2010.) Several species of shark other than whale sharks have also been observed to contain this sperm storage ability such as blue sharks and whitespotted bamboo sharks (Schmidt, 2010.) These specialized glands allow these sharks to store sperm and use it for fertilization at a later time. The fact that these sharks have this capability can lead to the assumption that whale sharks may also have this capability (Schmidt, 2010.)

After reading both the primary and secondary articles it can be seen that the secondary article highlights the most important points that exist within the primary article but lacks the detail of the primary article. However, a secondary article is not meant to explain the results of a study in such detail but rather summarize the key points. The secondary article did not make any claims that the primary article did not and thus it can be said that the secondary article provided a fair representation of the primary article.

Bibliography:

-University of Illinois at Chicago. "Whale Sharks May Produce Many Litters from One Mating, Paternity Test Shows." ScienceDaily 31 August 2010. 23 September 2010 .